New Caledonian Crows Can Combine Objects to Construct New Compound Tools

According to a new study published in the journal Scientific Reports, habitually tool-using New Caledonian crows (Corvus moneduloides) are able to create tools by combining two or more otherwise non-functional elements, an ability so far observed only in humans and great apes.

New Caledonian crow with a stick tool. Image credit: Auguste von Bayern.

New Caledonian crow with a stick tool. Image credit: Auguste von Bayern.

Assemblage of different components into novel functional and maneuverable tools has, until now, only been observed in apes, and anthropologists regard early human compound tool manufacture as a significant step in brain evolution.

Children take several years before creating novel tools, probably because it requires anticipating properties of yet unseen objects.

Such anticipation, or planning, is usually interpreted as involving creative mental modeling and executive functions.

New Caledonia crows are of the same species as Betty, who became famous in 2002 as the first animal shown to be able to create a hooked tool by bending a pliable material.

Ornithologists had already been able to show how these remarkable birds were able to use and make tools in the wild and in captivity, but they had never previously been seen to combine more than one piece to make a tool.

“Our results corroborate that these crows possess highly flexible abilities that allow them to solve novel problems rapidly, but do not show how they do it,” said study co-lead author Dr. Alex Kacelnik, from the University of Oxford.

“It is possible that they use some form of virtual simulation of the problem, as if different potential actions were played in their brains until they figure out a viable solution, and then do it.”

“Similar processes are being modeled on artificial intelligences and implemented in physical robots, as a way to better understand the animals and to discover ways to build machines able to reach autonomous creative solutions to novel problems.”

In the study, Dr. Kacelnik and colleagues presented eight wild-caught New Caledonian crows with a puzzle box they had never encountered before, containing a small food container behind a door that left a narrow gap along the bottom.

Initially, the scientists left some sufficiently long sticks scattered around, and all the birds rapidly picked one of them, inserted it through the front gap, and pushed the food to an opening on the side of the box. All eight birds did this without any difficulty.

In the next steps, the team left the food deep inside the box but provided only short pieces, too short to reach the food.

These short pieces could potentially be combined with each other, as some were hollow and others could fit inside them.

In one example, they gave the birds barrels and plungers of disassembled hypodermic syringes. Without any help or demonstration, four of the crows partially inserted one piece into another and used the resulting longer compound pole to reach and extract the food.

At the end of the five-step investigation, the researchers made the task more difficult by supplying even shorter combinable parts, and found that one bird particular bird, ‘Mango,’ was able to make compound tools out of three and even four parts.

“The finding is remarkable because the crows received no assistance or training in making these combinations, they figured it out by themselves,” said study co-lead author Dr. Auguste von Bayern, from the Max-Planck-Institute for Ornithology and University of Oxford.

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A.M.P. von Bayern et al. 2018. Compound tool construction by New Caledonian crows. Scientific Reports 8, article number: 15676; doi: 10.1038/s41598-018-33458-z

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